Melatonin is a hormone found naturally in the body. Melatonin used as a medication is usually done synthetically in a laboratory.
It is most commonly available in pill form, but melatonin is also available in forms that can be placed on the cheek or under the tongue. This allows melatonin to be absorbed directly into the body.
People use melatonin to adjust the internal clock of the body. It is used for time-shift syndrome, to adjust sleep-wake cycles in people whose daily work program changes (shift work disorder), and to help blind people set up a day and night cycle.